There are many methods for delivering airborne components, such as fragrances, insect repellents and the like. Scented candles, for example, are well know implements for delivering a desirable smell to the air. Incense performs essentially the same function, but the aroma is typically the natural smell evolved when the incense is burned. That is, incense typically does not require the addition of a fragrant component, while scented candles are generally a mixture of wax and a fragrance. In yet another variant of aroma delivering combustion devices, candles have been used to heat liquids or gels causing a volatile component to evolve. Moreover, lamps that burn oil have been used for ages, not only to provide light, but also to deliver fragrances. Combustion devices for delivering fragrances are well know, but most of these devices have also been used to deliver other airborne components, such as insect repellents, medicinal vapors such as eucalyptus, and other compounds.
Unfortunately, combustion devices inherently give rise to safety issues. They can be accidentally knocked over resulting in a fire, or when left unattended, many combustion devices can burn down to their base and ignite the surrounding surface. Moreover, smoke is an inevitable by-product of any combustion device. In general, smoke from a combustion device can be noxious, and may cause long term health problems. Thus, while these devices are simple and inexpensive methods for delivering airborne components, they are not without problems.
Another method of delivering airborne components is to simply rely on evaporation. For example, a liquid, solid or gel material that contains an airborne component can be placed anywhere and over time the airborne component will evolve to the surrounding environment via evaporation. But this system relies on the difference between the vapor pressure of the airborne component and atmospheric pressure. If the vapor pressure of the airborne component is too high, the component will be delivered to fast. Likewise, if the vapor pressure of the component is too low, the component will be delivered too slowly to make a marked effect in the surrounding environment. Many insect repellents, for example, cannot be delivered effectively by evaporation alone because of their high vapor pressure. Thus, evaporative devices are very limited in the type of material they can deliver, and the speed with which these select materials can be delivered.
Slightly more advanced apparatuses for delivering airborne components use electrical power from batteries or an electrical outlet in the home. These devices typically use the electricity to provide heat, forced air flow, or both to speed the delivery of the airborne component. Unfortunately, these devices are necessarily more complicated and expensive to build and operate than are combustion and evaporative devices. While these devices may improve delivery, they increase complexity and cost. Moreover, the devices that are not battery operated are inherently not portable as they require an electrical outlet.
Sprays and aerosols can deliver a wide variety of materials to the air. But these devices are, in general, manually operated and provide a short burst of the delivered component. Sprays and aerosols are not well suited for the prolonged delivery of a substance unless they are provided with a mechanical control mechanism. Such mechanical controls are expensive and limit the portability of such devices.
Self contained exothermic reaction mixtures that are initiated by the addition of an aqueous solution have been considered for delivering compositions to the surrounding air. A self contained exothermic reaction can provide heat without a combustion or an electrical source. The heat, in turn, can speed the evaporation of the composition that one wishes to deliver. As such, a wider range a compositions can be delivered in this manner. But these reactions have one substantial problem, they are hard to control. For example, it has been difficult to design a reaction system that is self contained, and runs at a constant temperature for an extended period of time. Likewise, it is difficult to design a reaction system that will run at one temperature for a first period of time, then change to a second temperature for a second period of time. It is axiomatic that one cannot control the delivery of the desired composition without controlling the temperature of the reaction system.
Thus, there exists a need for improved methods and apparatuses for delivering compositions to the surrounding air. These improved methods and apparatuses should overcome the problems discussed above. Specifically, they should not require combustion, and they should not rely solely on evaporation. There is a need for devices that deliver compositions to the air in a more controlled manner and for a longer period of time than aerosols and sprays. Moreover, these improved methods and apparatuses should be portable and relatively inexpensive.